1. Refrigerant: A 1991 Ford Tempo used R-12 (Freon 12) refrigerant. R-12 is an ozone-depleting substance and is no longer legally manufactured or sold in most places for automotive use. You will likely need to find a substitute like R-134a, but this requires significant system modifications including oil changes and potentially seal replacements. Using R-134a in an R-12 system without these modifications can damage the compressor.
2. Tools and Equipment:
* Manifold gauge set: This is absolutely essential for monitoring pressure and ensuring proper charging.
* Refrigerant (R-134a or a suitable R-12 substitute if you choose to make modifications): Again, consult a professional about appropriate substitutes and conversion if you choose this route. R-12 is almost impossible to legally obtain.
* Vacuum pump: This removes air and moisture from the system before adding refrigerant. Moisture is extremely damaging to AC systems.
* AC compressor oil (PAG oil for R-134a or mineral oil for R-12 if using a converted system): The type of oil is critical and must match the refrigerant.
* Leak detector (optional, but highly recommended): Before recharging, find and fix any leaks. UV dye can be added to the system to help identify leaks with a UV light.
* Safety glasses and gloves: Refrigerant can cause frostbite and eye irritation.
3. Procedure (General Outline - consult a repair manual specific to your 1991 Ford Tempo for details):
* Locate the low-pressure and high-pressure ports on the AC system. These are usually on the drier/accumulator.
* Attach the manifold gauge set to the low-pressure and high-pressure ports.
* Evacuate the system: Use the vacuum pump to draw a deep vacuum (near 0 PSI) for at least 30 minutes to remove moisture and air. This is crucial.
* If using R-134a in an R-12 system, you MUST flush and replace the system oil with the correct PAG oil for R-134a. This process is complex and often best done by a professional.
* Add refrigerant: Slowly add refrigerant according to the manufacturer's specifications (found in your repair manual). Monitor the gauges closely. The pressures should be within the specified range at different ambient temperatures (these are found in your repair manual).
* Check for leaks: After recharging, observe the system for leaks. Use a leak detector if needed.
Again, this is a simplified overview. Attempting this without proper training and equipment can damage your AC system, lead to injury, or void any warranties.
Strong Recommendation: Take your 1991 Ford Tempo to a qualified AC repair technician. They have the experience, tools, and refrigerant to handle the job safely and effectively. The cost of professional repair will almost certainly be less than the cost of potentially ruining your AC compressor or creating other costly problems.
